chore(claude-code): add project agent and quality-check hook config

Add the Explore subagent definition and a PostToolUse hook that runs
Ruff and ty on Python file edits, plus the settings.json wiring it in.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.claude/agents/Explore.md

@@ -0,0 +1,5 @@
+---
+name: Explore
+description: Fast, read-only codebase search
+model: sonnet
+---

.claude/hooks/python_quality.py

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+#!/usr/bin/env python3
+"""Run Python quality tools for Claude Code Write/Edit hooks.
+
+The hook is intentionally non-blocking: it formats/fixes what Ruff can fix safely,
+then reports remaining Ruff/ty diagnostics back to Claude as additional context.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import json
+import subprocess
+import sys
+from pathlib import Path
+
+PYTHON_SUFFIXES = {".py", ".pyi"}
+SKIP_PARTS = {".git", ".venv", "__pycache__"}
+
+
+def main() -> int:
+    payload = _read_payload()
+    file_path = _extract_file_path(payload)
+    if file_path is None:
+        return 0
+
+    repo_root = _repo_root()
+    path = _resolve_path(file_path, repo_root)
+
+    if not _should_check(path):
+        return 0
+
+    relative_path = _display_path(path, repo_root)
+    before = _sha256(path)
+
+    fix = _run(["uv", "run", "ruff", "check", "--fix", str(path)], repo_root)
+    fmt = _run(["uv", "run", "ruff", "format", str(path)], repo_root)
+    lint = _run(["uv", "run", "ruff", "check", str(path)], repo_root)
+
+    # `--error-on-warning` makes ty warnings visible to the hook while this
+    # script still exits 0, so warnings are reported but do not stop Claude.
+    types = _run(["uv", "run", "ty", "check", "--error-on-warning", str(path)], repo_root)
+
+    after = _sha256(path)
+    changed = before != after
+
+    message = _build_message(
+        relative_path=relative_path,
+        changed=changed,
+        fix=fix,
+        fmt=fmt,
+        lint=lint,
+        types=types,
+    )
+    if message:
+        print(
+            json.dumps(
+                {
+                    "suppressOutput": True,
+                    "hookSpecificOutput": {
+                        "hookEventName": "PostToolUse",
+                        "additionalContext": message,
+                    },
+                }
+            )
+        )
+
+    return 0
+
+
+def _read_payload() -> dict[str, object]:
+    try:
+        raw = sys.stdin.read()
+        return json.loads(raw) if raw.strip() else {}
+    except json.JSONDecodeError:
+        return {}
+
+
+def _extract_file_path(payload: dict[str, object]) -> str | None:
+    response = payload.get("tool_response")
+    if isinstance(response, dict):
+        for key in ("filePath", "file_path"):
+            value = response.get(key)
+            if isinstance(value, str) and value:
+                return value
+
+    tool_input = payload.get("tool_input")
+    if isinstance(tool_input, dict):
+        value = tool_input.get("file_path")
+        if isinstance(value, str) and value:
+            return value
+
+    return None
+
+
+def _repo_root() -> Path:
+    result = subprocess.run(
+        ["git", "rev-parse", "--show-toplevel"],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+    if result.returncode == 0:
+        return Path(result.stdout.strip()).resolve()
+    return Path.cwd().resolve()
+
+
+def _resolve_path(file_path: str, repo_root: Path) -> Path:
+    path = Path(file_path).expanduser()
+    if not path.is_absolute():
+        path = repo_root / path
+    return path.resolve()
+
+
+def _should_check(path: Path) -> bool:
+    return path.is_file() and path.suffix in PYTHON_SUFFIXES and SKIP_PARTS.isdisjoint(path.parts)
+
+
+def _display_path(path: Path, repo_root: Path) -> str:
+    try:
+        return str(path.relative_to(repo_root))
+    except ValueError:
+        return str(path)
+
+
+def _sha256(path: Path) -> str:
+    return hashlib.sha256(path.read_bytes()).hexdigest()
+
+
+def _run(command: list[str], cwd: Path) -> subprocess.CompletedProcess[str]:
+    return subprocess.run(
+        command,
+        cwd=cwd,
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+
+def _combined_output(result: subprocess.CompletedProcess[str]) -> str:
+    return "\n".join(part.strip() for part in (result.stdout, result.stderr) if part.strip())
+
+
+def _command_label(result: subprocess.CompletedProcess[str]) -> str:
+    return " ".join(result.args) if isinstance(result.args, list) else str(result.args)
+
+
+def _build_message(
+    *,
+    relative_path: str,
+    changed: bool,
+    fix: subprocess.CompletedProcess[str],
+    fmt: subprocess.CompletedProcess[str],
+    lint: subprocess.CompletedProcess[str],
+    types: subprocess.CompletedProcess[str],
+) -> str:
+    lines: list[str] = []
+
+    if changed:
+        lines.append(
+            f"Python quality hook updated `{relative_path}` with Ruff safe fixes/formatting."
+        )
+        lines.append("Read the file before making another manual edit to avoid stale text.")
+
+    for result in (fix, fmt, lint, types):
+        if result.returncode == 0:
+            continue
+
+        output = _combined_output(result)
+        if not output:
+            output = f"Command exited with status {result.returncode}."
+
+        lines.extend(
+            [
+                "",
+                f"Remaining diagnostics from `{_command_label(result)}`:",
+                "```text",
+                output[-6000:],
+                "```",
+            ]
+        )
+
+    return "\n".join(lines).strip()
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

.claude/settings.json

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+{
+  "enabledPlugins": {
+    "astral@astral-sh": true
+  },
+  "hooks": {
+    "PostToolUse": [
+      {
+        "matcher": "Write|Edit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "repo=$(git rev-parse --show-toplevel 2>/dev/null || pwd); python3 \"$repo/.claude/hooks/python_quality.py\"",
+            "timeout": 120,
+            "statusMessage": "Running Ruff and ty on Python edit"
+          }
+        ]
+      }
+    ]
+  }
+}